Loopers for sewing machines



April 1956 'D. B. SCOTT 2,740,366

LOOPERS FOR sswmc MACHINES Filed Aug. 28. 1953 2 Sheets-Sheet 1 ig. I.

3 u xx m on 20 F; 24 23 m v k IO zzvmvrozz. David B. Scott BY ATTORNEYApril 3, 1956 D. B. SCOTT 2,740,366

' LOOPERS FOR sswmc MACHINES Filed Aug. 28, 1953 2 Sheets-Sheet 2INVENTOR. DCIVid B. Scoh WITNESS BY WK A QA W4 ATTORNEY Loornns nonSEWING MACHINES David B. Scott, Plainfield, N. 5., assignorManufacturing (fompany, tion of New Jersey Application August 28, 1953,Serial No. 377,167

3 Claims. (Cl. 112-400) to The inger Elizabeth, N. .I., a corpora- Thisinvention relates to a thread-carrying looper for a two-threadchain-stitch sewing machine.

'An object of this invention is the provision on a 3 threaded looper oflooper-thread guarding surfaces which are formed and arranged to obviateobjectionable interference between the looper-thread and theneedle-thread during stitch formation.

Other objects and advantages will be apparent from the followingdescription and accompanying drawings of a preferred embodiment inwhich:

Fig. 1 is a fragmentary front elevational view, partly in section, of atwo-thread chain-stitch sewing machine .-.having portions broken away toillustrate more clearly the thread-carrying looper and the looperactuating mechanism,

Fig. 2 is a front elevational view of the looper, Fig. 3 is an enlargedrear elevational view of the blade portion of the looper,

the position of parts and proper thread concatenation during loopseizure by the looper on the upstroke of the needle,

Fig. 7 is a cross-sectional view taken substantially along line 7-7 ofFig. 6,

Fig. 8 is a perspective view similar to Fig. 6 but illustrating animproper concatenation of thread as obtained frequently with a looper ofusual construction, and

Fig. 9 is a cross-sectional view of the usual looper taken substantiallyalong line 99 of Fig. '8.

Referring to the drawings, Fig. 1 illustrates a portion of a sewingmachine having a frame including a bed 10 formed with a work-supportingcloth plate 11 which car- 'ries the usual throat-plate 12. Overhangingtheibed is a gooseneck terminating in a sewing head 13 in which isjournaled an endwise reciprocatory needle-bar 14, which carries a needle15, and a presser-bar 16 to which is fitted a presser-foot 17. Rotatablyjournaled beneath the work-supporting cloth plate is a bed-shaft 18which serves to impart a so-called four-motion path of movement to athread-carrying looper 19 which thereby cooperates with thereciprocatory needle in the formation of two-thread chain stitches. Thelooper 19 is fixed to a carrier member 20 which is journaled foroscillation on a transverse stud 21 carried by a rock-shaft 22 which inturn is journaled in the bed 10 parallel to the axis of the bed-shaft.

Oscillation of the looper carrier about the transverse stud 21 providestwo of the four looper motions, a needle-loop seizing movement, asillustrated in Figs. 6 and 8, and a loop-shedding movement, as shown inFig. 5. Loop-seizing and -shedding movements are derived from a crank 23on the bed-shaft 18 and are transmitted to United ates Patent of course;important.

ice

description of the looper-actuating mechanism, reference may be had tothe U. S. March 28, 1944.

Theconstruction of my improved looper is best'illustrated in Figs. 2, 3and 4. The looper is providedwith a base portion 30 from which dependsuastud 31'which is slabbed as at 32 so that the looper may be securedandproperly located in the carrier 20 as by means'of a set patent ofClayton, No. 2,345,327,

screw. A looper blade 33 extends over the base portion and is joinedthereto by a heel portion 34- which is formed with a thread-guidingeyelet 35 through which a looper thread is directed. The front face ofthe. looperblade, as viewed in Fig. 2, is formed with a thread-guidingslot 36 which extends from the eyelet 35 to an eye 37. At

'the rear face of the looper, which is best illustrated in Fig. 3, ashallow'and substantially vertical notch 38 is formed in the looperblade leading'directly to the eye 37. .T he rear face of the looper'isformed with a threadguarding recess-39 which extends lengthwise of thelooper blade from a point adjacent the eye 37 toward the heel of thelooper. As best shown inFig. 4, the thread-guarding recess 39 is formedat a point nearer the bottom. surface 40 of the looper thanis thethreadeguiding slot 36 in the front face. The recess 39, moreover, ispreferably formed over most of its length with substantially parallelsidewall portions 4141.

In the successful formation of two-thread chain stitches, properinterrelated movements of looper and needle are, However, it is of equalimportance, particularly athigh rates of.sewing speed or when sewingconditions change rapidly as instarting or when a crossseam orobstruction is encountered, that proper concatenation of looperandneedle threads be maintained at the various critical points in. thestitching cycle. Interference between the needle and looper threads is a;primary source of improper thread concatenation, for

.mal control and, therefore, do not concatenate properly at succeedingcritical points 'in the stitching cycle, thus resulting in frequentthread breakage and loose or skipped stitches.

Figs. 5, 6 and 7 depict the relationship of looper and needle at twocritical points during a cycle of stitch formation and illustrate themanner in which my improved looper serves to insure proper or desiredconcatenation of threads at each of these points. Figs. 8 and 9illustrate the usual form of looper and show how thread interferenceoccurs therewith. In these views, a needle thread is indicated as nwhile a looper thread is designated l. The arrow marked F indicates thedirection in which the work is being fed while the arrow N shows thedirection of needle reciprocation in each view. In Fig. 5, the arrow Lindicates the direction of needleavoiding movement of the looper, whilethe arrow L shows the direction of loop-shedding movement thereof. InFigs. 6 and 8 the looper is partaking only of loopseizing movement thedirection of which is indicated by arrow L In Fig. 5, the needle isshown descending through the work and the throat-plate rearwardly of thelooper. The

combined effect of the feed of the work and the needleavoiding movementof the looper in the opposite directions results in the formation of athread triangle for entrance by the needle. The thread triangle consistsof one limb of looper thread extending from the work to the looper eye37, a second limb of looper thread extending along the looper in thethread guiding slot 36, and the needle-thread loop of the previousstitch which is being shed by the looper. Of these parts of the threadtriangle, the limb of looper thread from the eye 37 to the work isperhaps most critical. If this limb of thread is not properly controlledso that it does not extend in a substantially direct path between thework and the looper eye, as shown in Fig. 5, proper stitch formationwill not occur. In particular, abnormal slack in the looper thread fromthe eye of the Work may cause the thread triangle to collapse and theneedle in failing to penetrate the collapsed thread triangle will skipthat stitch and thus produce a defective seam which may be unraveledeasily.

In Figs. 8 and 9, a looper of usual construction is illustrated having arear face 42 which is smooth and not provided with the thread-guardingrecess 39 as in the looper of the present invention. In these figures,the looper occupies a position immediately after seizure of theneedle-thread loop. As shown in the drawings, the limb of looper threadfrom the eye of the looper to the work must pass through the needle loopat this point. While this limb of looper thread is passing through, theneedle loop is being drawn up by-the ascending needle so that theneedle-thread loop is, in effect, being turned in a counterclockwisedirection about the looper blade as viewed in Fig. 9. With a looper ofordinary construction, the looper thread is frequently caught up by thetightening needle-thread loop and carried with the needle thread in acounterclockwise direction about the looper, thus creating an abnormalbight in the looper thread which in the succeeding position of Fig. 5results in a slack limb of looper thread from the eye of the looper tothe work.

Referring to Figs. 6 and 7, my improved looper is illustrated togetherwith the proper concatenation of thread which is dictated thereby.Should the looper thread be caught up by the tightening needle-threadloop, the looper thread will be carried into the thread-guarding recess39 on the rear face of the looper blade, rather than being carriedabnormally under and about the looper blade. As the needle-loop shiftstoward the heel of the looper, the undistended limb of looper threadfrom the looper eye to the work will, therefore, assume a direct andproper path without objectionable slack.

The thread-guarding recess 39 is illustrated in Figs. 2, 3 and 4 in itspreferred form. It is located beneath the level of the guide slot 36 andthe looper eye 35 so as to be in position to receive and protect thelooper thread should it be caught up by the needle-thread loop. The sidewalls of the recess 39 are preferably made substantially parallel toeach other and are disposed substantially perpendicular to the rear faceof the looper blade. By this construction, no projecting shelf or ledgeis presented which might be struck by the needle point.

Having thus set forth the nature of the invention, what I claim hereinis:

l. A thread-carrying chain-stitch looper having a blade provided with afree extremity, said blade formed with a transverse thread-accommodatingeye adapted to receive a thread from one side of said blade and deliversaid thread to the opposite side thereof, said blade being formed with athread-guarding slot arranged substantially lengthwise of said blade,said slot being disposed to extend away from said free extremity from apoint spaced not more than the width of said thread-guarding slot fromthe delivery end of said thread-eye.

2. A thread-carrying chain-stitch looper having a blade formed with afree extremity and a looper supporting heel extremity a transversethread-eye formed in said free extremity, said blade being formed at oneside with a thread-guiding slot adjoining said thread eye and adapted todeliver a limb of thread from a supply to said thread-eye, said bladebeing formed at the opposite side with a thread-guarding slotterminating at a point not more than the width of said thread guardingslot from said thread-eye and adapted to accommodate a limb of threadextending from said thread-eye, each of said slots extending fromadjacent to said thread-eye toward the heel extremity of said blade.

3. A thread-carrying looper for a chain-stitch sewing machine having areciprocatory work-penetrating needle and means actuated by said sewingmachine for shifting said looper in timed relation with said needlereciprocation, said looper comprising an elongated blade having apointed free extremity formed with a transverse threadeye adapted toreceive a looper-thread at one side of said blade and deliver saidthread at the opposite side thereof, said looper-blade being formedadjacent the thread delivery side thereof with a looper thread guardingslot extending lengthwise of said looper-blade from a point not morethan the width of said thread guarding slot from said thread eye and ina direction away from the free extremity of said blade, saidthread-guarding .slot having parallel side-Wall portions disposedsubstantially perpendicular to the path of reciprocation ofsaid needle.

References Cited in the file of this patent UNITED STATES PATENTS1,115,086 Moffatt Oct. 27, 1914 FOREIGN PATENTS 6,037 Great Britain 1912

